1. Field of the Invention
The present invention relates to a dental adhesive composition to be used for adhering a dental restoration material to a tooth structure. More particularly, the present invention relates to a one-pack type dental adhesive composition capable of surely adhering both of a dental restoration material and a tooth structure and keeping an adhesive effect over a long period of time through a simple operation in which a plurality of operation steps are not required during the use as in the conventional art and in which mixing of two or more multiple components are not required in one step, in case of adhering a dental restoration material such as filling composite resins, filling compomers, fissure sealants for pit and fissure block out, root coating materials, lining materials, and resin cements, to a tooth structure such as an enamel and a dentin.
2. Description of the Conventional Art
With spreading of dental restoration materials such as composite resins, dental adhesive compositions from which a strong adhesive effect is obtained through a simple operation are being demanded to adhere a dental restoration material to a tooth structure. With respect to the conventionally employed dental adhesive compositions and methods for using the same, is generally employed a method in which a tooth structure is etched with an acid such as phosphoric acid and citric acid, is then subjected to priming treatment with a primer containing an adhesive monomer or a hydrophilic monomer for enhancing the adhesive properties, and is further adhered by a bonding agent as an adhesive. However, this method was complicated in terms of the adhesion operation step because it requires three steps of etching treatment→priming treatment→bonding agent application treatment. Further, according to this method, though the adhesive properties to an enamel are high, it could not be said that the adhesive properties to a dentin are satisfactory.
In recent years, there was developed a two-step system in which the adhesion is carried out by using a self-etching primer, with which the etching treatment and the priming treatment can be carried out at the same time, and a bonding agent, that is, this two-step system is comprised of two steps of self-etching treatment→bonding agent application treatment. Also, recently, a one-step type adhesive composition that does not require a pre-treatment such as an etching treatment and a priming treatment but applies only a bonding agent application treatment is disclosed in Japanese Patent Laid-Open No. 2000-159621 and the like. However, since this adhesive composition basically acts as a primer, actually it requires a bonding agent separately. As described above, the currently commercially available two-step system type dental adhesive compositions or those that are in fact of a two-step system type but are called as a “one-step type” involved a defect that the operation is complicated.
Further, Japanese Patents Laid-Open Nos. 10-245525, JP-A-11-140383 and 2001-72523 propose one-step type adhesive compositions that do not require a pre-treatment such as an etching treatment and a priming treatment. However, in any of these cases, although these patents do not definitely describe, there was involved a defect that in order to obtain the required adhesive properties, a multiple components-mixing type catalyst is needed as a catalyst in addition to a photo-polymerization catalyst, and hence, two or more components must be in fact packed and stored separately from the standpoint of preservation stability. For this reason, the respective components must be mixed at the time of use, and though the adhesion operation itself is of a one-step system, the mixing operation is required at the time of use. Accordingly, there was a defect that the operation is complicated.
Moreover, Japanese Patent Laid-Open No. 2001-26511 discloses an adhesive composition comprising an acidic group-containing polymerizable compound, a water-soluble film-forming agent, water and a curing agent. This adhesive composition is of a one-pack type, which does not require a pre-treatment such as an etching treatment and a priming treatment. The film-forming agent containing 2-hydroxyethyl methacrylate as a major component, as used in this adhesive composition, is characterized in that it can be admixed with physiological saline water. However, such composition containing a large amount of a highly hydrophilic, polymerizable monomer such as 2-hydroxyethyl methacrylate involved a problem in durability. That is, when in actual clinics, the composition stays for a long period of time within an oral cavity, a polymer elutes out from a so-called hybrid (resin-impregnated) layer as a layer formed by polymerization and curing generated after highly hydrophilic polymerizable monomer component penetrates into a tooth structure, whereby leakage of edges and drop-out likely occur. In addition, it is worried about to use the composition containing a large amount of 2-hydroxyethyl (meth)acrylate from the standpoint of an allergy.
As discussed above, any dental adhesive composition which is practically useful and is of a one-pack type and that does not require a mixing operation during the use has not yet been obtained. Accordingly, a novel reliable dental adhesive composition whose operation is simple and which is stable in terms of an adhesive effect within an oral cavity over a long period of time has been demanded.